Carbon Tool Steel
The steel grade is prefixed with "T" to avoid confusion with other types of steel.
The number in the steel grade indicates the carbon content, expressed as parts per thousand of the uniform carbon content. For example, "T8" represents a uniform carbon content of 0.8%.
For steel with a higher manganese content, "Mn" is marked at the end of the steel grade, such as "T8Mn".
High-quality carbon tool steel has lower phosphorus and sulfur content than regular high-quality carbon tool steel. To distinguish it, the letter "A" is added at the end of the steel grade, for instance, "T8MnA".
Carbon Structural Steel
It is composed of "Q" + a number + quality grade symbol + deoxidization method symbol. The "Q" prefix represents the yield point of the steel, and the subsequent number indicates the yield point value in MPa. For example, Q235 represents carbon structural steel with a yield point (σs) of 235 MPa.
When necessary, symbols indicating quality grade and deoxidization method can be marked after the steel grade. The quality grade symbols are A, B, C, D. The deoxidization method symbols are F for rimming steel, B for semi-killed steel, Z for killed steel, and TZ for special killed steel. Killed steel may not be marked with a symbol, meaning both ZT and TZ can be omitted. For example, Q235-AF represents grade A rimming steel.
For special-purpose carbon steel, such as bridge steel and ship steel, the representation method of carbon structural steel is generally adopted, with additional letters indicating the intended use added at the end of the steel grade.
High-Quality Carbon Structural Steel
The first two digits of the steel grade indicate the carbon content, expressed as parts per ten thousand of the uniform carbon content. For instance, steel with a uniform carbon content of 0.45% has a steel grade of "45", which is not a sequential number and should not be read as "Grade 45" steel.
For high-quality carbon structural steel with a higher manganese content, the manganese element should be indicated, such as 50Mn.
Rimming steel, semi-killed steel, and special-purpose high-quality carbon structural steel should be specifically marked at the end of the steel grade. For example, semi-killed steel with a uniform carbon content of 0.1% has a steel grade of 10b.
